Process for the purification of piperidine



PROCESS FOR THE PURIFICATION OF PIPERIDINE Filed May 8, 1945 A 'TTORNE Y 1 f o dine and pyridine.

pear hereinafter..` i

Patented Nov. 2l, 1944 r o o `2,363,158 o i f `PROCESSFOR THE rUmFIcA'rioN oF Henry4 L. .Stassqiliawthorna N. J., assigner to Allied Chemical & Dye Corporation, New York, '1i Y., a corporations-of Nett7 `York i e i 1 l Aplietienfmey 8,(1943, serial no'. 486,254.`

piperidine from pyridinefand more particularly piperidine associated'with pyridine." t

In the production of piperidine by lhydrogena? tion of pyridine,` reaction'jmixtures "constituted predominantlyof piperidine and containing substantial proportions, egg.; ,5"to per cent by piperidine` and atlleast Sper `cent"ofpyrldine p boiling at about 106,1 C. at atmospheric pressure "(760 mm. of mercury). Hence,opiperidine subt `stantially free from pyridine cannot `be obtained by conventional fractional distillation of piperidine-pyridine mixtures. i f

It isanuobjcct olthefinvention to provide a d to aidistillation` processforlthe` puricationgof n employed, the water layer is returned to the still `during the distillation. d p y p Distillation `of`piperidinefpyridinemixtures in lthe presence of water and the above mentioned i hydrocarbons yields water1hydrocarbon-'piperidine-pyridine azeotropic distillates containing a higher ratio of` pyridine to piperidine than is present in the still charge, thereby leaving a residue enriched in .piperidine The fact that the azeo-` tropic distillatesl contain relatively high ratios of pyridine to piperidine permits progressive removal of `pyridine as distillate. g d

Purification of piperidineby azeotropic distillael i `tion in accordance with the invention may be etlectedto greatest advantage utilizing piperi" i `dine-pyridine mixtures containing about 80 to 95 distillation process `for the recovery "of relatively o.

pure piperidinefrom mixtures containing piperi- It is afurtner object of vide an economical process of separating piperidine from mixtures containing t piperidine and pyridine by distilling oil the pyridine asan azeotropic mixture containing Water.` i

the invention to proy. r

It is another object of` theinventionto provide a process for simultaneously removing pyridine.y

from and dehydrating waterepiperidine-pyridine mixtures. Otherobjects and advantages will apo In accordance with `the invention, mixtures containing piperidine andlpyridine Aare fractionally distilled in the presence of water and non` aromatic hydrocarbons capablelof `forming azeotropic mixtures containing thewater, hydrocarbons and a relatively high ratio` of pyridine to piperidine,` which azeotropic mixtures "boil Below the `boiling `point n of pyridine,`partioularly1 aliphatic and alicycllcQhydrocarbons boilingV within the range of90f to/105 C; In carrying vout the process, a relatively large amount ofvslater` and o small amounto'f `the hydrocarbong;oruasmall` amount of water andlarge amount'` oi hydrocar-` bon. `or. any desired intermediate proportions oi-` o. Water and hydrocarbon may be utilized." The dis-` tumedto the stuluntn the desired purification of the piperidin'e is 1eiected;` `when a large amount of hydrocarbon and Ia` small amountr of water is"` `percent of piperidine and 5 to 20 per cent pyridine n based on the weight of themixture. `By utilizing such mixtures yhighyields of vpiperidine of a purity of 98 per cent by weight or higher are readily ob-` tained. When it is desired to employ mixtures containing more than about 20 per` cent of pyridineVthey are preferably fractionated by nonazeotropic `fractional distillation to obtain frac- U tions of piperidine content ofat least BOper cent by weightprior to azeotropic distillation. Piperidine-pyridine mixtures containing materially less than per cent of piperidine may also be azeo l tropically distilled inaccordance withthe invention toobtain piperidine of to98 per cent or higher purity.` When mixtures of low piperidine content, say lower than 30 per cent based on the fractional distillation prior to an azeotropicdistillation. o f o As the hydrocarbon material, either substantially pure hydrocarbon compounds orhydrocar- .bon mixtures may be utilized. suitable hydro- I carbons include aliphaticsaturated and unsaturated, straight and branched-chain hydrocarbons, alicyclic unsaturated hydrocarbons and cycloparaifins', jfor example 3-rnethylhexane,` n-hep`- tane, cyclohexane, 1Ll-dimethylcyclopentane, 1,2- dimethylcyclopentane, lfdirnethylcyclopentane, cyclohexene, cyclohexadiene, methylcyclohexa` diene," difisobu'tylena methylcyclohexane, and petroleum'fractions constituted predominantly of para'fnnic,` olenic or naphthenic compounds, or mixtures thereof, boiling within the desired boiling range. I prefer to employ aliphatic and naphthenic hydrocarbons as azeotropic agents. At

leasta substantial portion, preferably all, of the hydrocarbons should boil within the range oi 80 to C.; preferably/from 90 to .105` C. `In

l i o y 2,363,158, n d uNrrEolsTArs PATENT oFFlcE general, the lower the boiling point oi' the hydrocarbon, the greater the amountl required to effect separation as aqueous distillate of a given amount of pyridine; on the other hand, hydrocarbons of higher boiling point than are distilled oif during removal of the aqueous azeotropic distillate containing pyridine are diilicult 'to remove from the piperidine residue. Hence, in preparing hydro carbon fractions for use in accordance with the invention, it is preferable to exclude from the fractions undue amounts of hydrocarbons boiling too low for economical separation of pyridine as aqueous azeotropic distillate and hydrocarbons boiling too high for removal as distillate during removal of the pyridine. i

The accompanying drawing is a; iiow sheet illusfew per centof water as a ,benzeneiwateuazem tropiodistillate. `After all of the water an .hy-

rocarbon arey removed from still I, the purified' piperidine remaining as residue may be distilled oil` and collected.

The azeotropic hydrocarbon yand aqueous distillates may be treated in any suitable manner to separate the pyridine and piperidine therefrom. For example; the initial portion of the hydrocarbon distillatetcontaining a higher ratio of pyridine vto piperidine than 25 to 75 may be azeo-t, `tropically distilled in the presence of methyl alcohol or ethyl alcohol to drive'oi the hydrocarbontand valcohol as azeotropic distillate leaving trating diagrammatically an arrangement of conventional apparatus which may be employed in carrying out the invention.

In the'drawingreference numeral I designates a still equipped with aV fractionating column 2.

Valved pipe's'3, 4 and Spare inlets through which piperidine-pyridine mixture, water and hydrocarbon material, respectively, may be introduced into the still. Vapors from the fractionating column dischargeinto condenser 1, communicating with a conventional separator 8`constructed to permit separation of the distillate from the condenser into a hydrocarbon layer and an aqueous layer and return of any desired proportion of either or both layers to column 2 through valved conduits lIll and II, the remainder of the layers lloing withdrawn through valved conduits I3 and The invention maybe carried out by charging a mixture containing piperidineand from 5 to 20 per cent by, weight of pyridine into still I together with from 5 to 200 per cent of water and 300 to 10 percent of hydrocarbon material based on the volume of the piperidine-pyridine mixture and azeotropically distilling the still charge. `An azeotr'opicI w a t e r-hydrocarbon-pyridine-piperidine distillate containing a higher ratio of pyridine to piperidine than the stillv charge is driven off, the distillate -vapors are condensed in condenser'l and the condensate is discharged into separator 8 which may be .set to return any desired proportions of the aqueous and` hydrocarbon layers to the column 2 to furnish reflux and maintain equilibruim withinthe column.

The proportions of thek aqueous and hydrocarbon layers returned to the column depends on the proportions of Awater and hydrocarbon in the as residue a pyridine-piperidine mixture which may be fractionally distilled to concentrate the piperidine or rehydrogenated. ,Therhydrocarbon andalcohol may readily be separated into layers and recovered for re-use. aqueous vdistillate containing a higher ratio of pyridine to piperidine than 25 to 'l5 may be dehydrated by azeotropic distillation in the presence y of benzene leaving pyridine-piperidine residue jwhich may be fractionally distilled to concentrate Y thel piperidine'or rehydrogenated. The portions f ofthe hydrocarbon and aqueous azeotropic distillates containing higher .ratios of piperidineto pyridine than to 25 may be charged into the still withla subsequent batch of piperidinepyriy dine mixture.

yIn a modiiied'fo'rm of the invention, instead-- of mixing the piperidine-pyridine mixture simultaneously with water and hydrocarbon, the mixture may be rst distilled inthe presence of waterv alone to obtain ainkaqueous azeotropic distilate containing between about x`and 97 parts by weight of piperidine toeachpart oi' pyridine and this aqueous distillate thenV az'eotr'opically distilled in the presence oi' a suitable noriaromatic 40 hydrocarbon.' AAdistillate containing the water,

still charge.I If the still charge contains an ex- Y cess of water, i. e., a. greater ratio'oi.' water to hydrocarbon than is present in the distillate, all or at least a suiiicient portion of the hydrocarbon layer is returned to the column to maintain azeotropicequilibrium with the water, pyridine and piperidine therein. On the other hand, if the still charge contains an excess of hydrocarbon, all or a suiiicient portion oi thel'aqueous layer to provide the desired azeotropic equilibrium is returned to thec'olumn. A portionV of the hydrohydrocarbon and-a high ratio orpyrldlne to piperidlne ,isl dri-venoi leaving a residue-constituted ofpiperidinebf 98 per cent orghigher purity. l i

The-following examples are, further illustrative of the-invention: y

L Example 1 `-reaction mixture obtained; by hydrogenating pyridine wasdistilled to remove ywater andy high boilingv compounds such as dipiperidyls; the re sultant product contained about 89 percent by weight of `piperidine, 9.5 percent of pyridine and 1 per cent of aliphatic amines calculated as amyl-' parts by. volume of this mixture were chargedwith 65 parts by volume `of a petroleum e amine.

distillateiraction boiling within` the range oi' from 90.89 'to 93.8, C. constituted of straight and y branchedf chain l,hydrocarbons and` 220 parts by volume of water into a still having a fractionat l ing column` equipped with a head arranged to separate the condensate `into two layers and re-v turn any desired `proportion of either` or both layers to the column.` r The still charge was azeof" tropically distilledA While returning all of the hydrocarbon layer of they condensed 'distillateand about 50 per cent `of` the aqueousylayer to the column, the remainder of the aqueous distillate being withdrawn from the apparatus.

except 3 to 5 parts by volumev of the `water werek removed from the still, the hydrocarbon layer was alsowithdrawn from the apparatus andremoval of residual water from the still was completed by adding 5 parts by volumeof benzene Y to the still and continuing the distillation where- The initial portion of i When all I 43 parts by volume of water were by thewater Wasdr azeotropic mixture. Dataon .thel azeotropicdisf tillation of `petroleum `hydrocarbonf-,W'Ster-piperi; dine-.pyridine mixture are given in the follovving,

table, the ratios be1ng byweight:

Total distillate v withdrawn (parts Ratio of Vapor by volume) we ter and Baticio' i i emperv oj `pipeii a. Frwuon ature, car onto to pyridine` C Water-and v basesin infraction hydro. Bases` fraction 4 carbon 76.6 38.0 2.0` 95:5 10:90 76. 6`. 76. 0 4.0 95:5 i 13:87" 76. 6 95. l 4.9 95:5 16:' 76.6'. 114.2 5.8 95:5 18u82` 76.8 133.4. i 6.6 961i` 18: 76. 8 152. 6 7. 4 97:3 21:79` 76.8 172.0 8.0 97:3v i 285.722 76. 8 191.l 5 8. 5 97.3 {42:68} 76.8 215. 8'. 9.2. 98:2 40:60r 77.0 254.3 10.`7` 95:5 60:40l 92.0` 280.0 1 2. 0 92:8 1:10

In fractions 1 to 9, inclusive,` thedistillate `withf drawn from` thestillwas constituted oflwaten pyridine and piperidine, and 11 thev withdrawn distillate was cons petroleum hydrocarbons, pyridineA and l piperidine.

The still residue amounted yto 78;` parte hyvoluine` of piperidineV of 98.5 per cent purityfcontaining per cent bywweight vof lpyridine and .5 per centro! aliphatic amines' calculated as amylamine, repreg senting recovery of `86 per` cent of the piperidine content of the original still charge. An` additional 10 per cent` of thepiperidine could be recovered azeotropically distilling fractions numbers 10 and;` 11 with a subsequent batch `of piperidine-.pyridine mixture. The pyridine and piperidine presentin` fractions 1 to 9 maybe recoveredinjany desired in .fractions 410. and r tituted` o!` in the` presence of as a benzene-water azeotropic distillate Withben.- zene and then iractionating or` rehydrogenatinge the pipe ridine-pyridi ne` residue. .i

Example 2 100 partsby volume of ciudepiperidlne andiioil parts byvolume of petroleum distillateboth signe-.1 lar to the materials employed'in Examplel, and

` distilled inthe. employed in Example 1 The, hydroy carbon-pyridine-piperidine layer was removed from the apparatus andthe aqueous layer was re-` turned to the column. Theratio of pyridinemo piperidine in the hydrocarbon layer was particuf larlyhigh (about 96:4)` during. the early stagesT of thefdistillation. A fter removal of the hydrocarbon and water.- a stillresidue containing piper-A idine of98 percent or higher purity remains, The l pyridine andpiperidine present .in` the hydrogen-, bon distillate `may be recovered by azeotropicdisf tiliation of the distillate in the pre or ethyl alcohol.` 1f desired, the distillate richer in piperidine may cally distilled with a subsequent batch of piperidne-pyridine mixture. A

. Example 3 A pyridine hydrogenation produ ally distilledl to free it fr stituents and high boiling constituents such as., dipiperidyls. 100 parts by volume of the .distilled` product containing about 90.8 per centby weight of piperidine, 7.9` per cent of pyridine andi per. cent of aliphatic amines calculated as amylamine were charged with 240 parts by v apparatus portion of the.

ct fraction,-

e o1 water into cyclohexane and 5 parts by volum sence oi methyl 60 om low boilingA cone p olume of methilaus.

a.stili.;similaritetiatwhen111.Bramble1- and themirturerwa @anni t Th` 1.

all 0f.; the methvlexelw.

Parts byvolume in Weight. total distillata` l ratiowoi Weight Vapor` hydro-1 ratiooi. Fraction tempera:l carhonand` Vpiperidine turegC." Methyloy--` waterto top'yridne i. cloheiane Bases basesin infraction andwater. i. i fraction 79.17` 57.2. i 2:8 .90:4 14=so 4 79.7 76,4 3.6.` 96:4 17:83

s... 80.0 95.15;` 4.5 j95.5r4.'5 27:73 i o.. n 10.0` 114;.5 5:5 95.5` 31:69 7 79.7 133.5; i 6,7 v 94:6` 51:491. 8. 79.8 152.0" 8.0. V93.5566 62:38 9,. 80.0` 170.16` 9.41: 93:7. 74:%. 1o. 50.0 181m` `10.8 93:7 144:16` V1l 80.1 207 8Q,;` 1.22 93:7 90:10 l2. 80.l. 226.51' z 13.5 i, 93.5565 94:6 13. 80.1` 235.18` 1422". "93:7- 95:5y 14. 90.0, 242.3;9 i 14.7" l 93:7" 95:5

1,5. 92.2, 245:7. 20.3 305.70 16. 1` 97.2. 246.7` 2&3 20,:801 17 106-6 247.15 aast 9191; ,H-.iia -106.75 247.25.. 33.75 imac Fractions 1' to. lrginclusive, were.,.constituted` or methylcyclohexane and-bases, .fractionsl5 and u 161contained `substantiall alli ofi thewater. in the` f still: ch p rse.l and.- fractions 17- and` 18; contained the residual:methylcycloheirane.- i

The still residue wasconstitutedfor iigparts by volume off piperidine 'or ifellper cent .purityuconf taining. .3 .per cent. my rjir linev and ..6fper cent of .i i aliphaticammesaleulaiedesemylwiiee. repre! seating about-'10 per; @et of? the? rivendica one watOfthariinal#immersa 'Anadditianal 20 per; cent ot the-. o ri g ir ia1 piperidinefis` recoverable byazeotropioally distiiling.fractionsyio tcl8 with i asubsequent-batch `l=piper idht-pif.liline InXr ture. The piperidine. andpyridinelcanfibe recovered fromfractionsi to,9 .jby aa'eotropic dis.-` tillationin thepresenceor ethylonethyl alcoss hol, whereby the., hydrocar. ril andualohol are. drivenA Ofi. as dliiilabeedi.marbesparared into. 1ayers for refuse; thepiperidineand pyridine remameeSti11;-re$1duf i Eeuwig 4 2 00 `partsby volumeof piperidinefpyridine ming ture. similar" to.. thatv employed inl Example 1 were charged with 135 parts byvolurne of=water into a. still. andthemi t e was fractionally distilled until 235 'jparts`by volume of. distillate containingf- '157,'.5 parts by. volume of pifp eri :iir1. `e including` l aliphatic amines, 4.5.parts by volume of pyridine, p and Z3 parts by volume of` water were obtained:I This distillate was charged-into a 'stilis iifriilalr.` tof that employed in Example 1 together-with 80; parts by volume of methylcyclohe'xane andthe mixture' was azeotropicallydistilled. The distil-l late was separated into an aoueousiayer anda methylcyclohexaneilayer. 'I 'heaqueous layer was `75l removed from the `fraetionati n g column and the" vofi as'an azeotropic mixture.

the

the column and distilllng until water was exhausted from the f The methylcyclohexane was then removed '-1 rparts by volume of ethyl alco` f the methylcyclohexane and alcohol were driven A Thestill residue was constitutedv of 150r parts b idine of 98.1 percent purity containing 1.1 per cent of pyridine and .5. per cent of aliphatic amines calculated-as-amylamine. i

Thus lit will be seen the inventionprovides a novel process ofpurifying piperidine present in mixtures-'containing piperidine and pyridine by azeotropicv distillation of the mixturesin the presence' of'vvater and non-aromatic hydrocarbons so that azeotropic mixtures containing pyridine are driven off as distillate leaving aresidue enrichedin piperidine. rThe process is highly iexible, permittingV the use as azeotropic agents of widely varyingfproportions of hydrocarbons andl water, thus` permitting the invention to be adapted to varying conditions such as the'availability of suitable hydrocarbons. While the invention is carried out batchwise in the above examples, it may also be carried out in a continuous manner.

Since certain changes departingl from the scope of vthe invention, it is intended that the aboveshall be interpreted as illustrative and not in a limiting sense.

What isclaimed is: l

1. A process of separating piperidine from pyridineswhich comprises ldistillinga mixture containing piperidine and pyridine andrectifying the vapors evolved therefrom in the presence of water and non-aromatic hydrocarbon material boiling within the range of 80 to 110 C. capable` of forming an azeotropic mixture containing the water,` hydrocarbon anda higher ratio o1' pyridine to piperidine than is present in the mixture being distilled, saidazeotropic mixture boiling belowv the boiling point of piperidine. f

volume of piperi azeotropic mixture containing the hydrocarbon,

2. A process of separatingr piperidine froml pyridine which comprises distilling azmixturecontaining piperidine, pyridine, water and non-aromatic hydrocarbon. material boiling within the 3. A process of separating piperidine from'pyridine which comprises distilling a mixture lcontaining piperidine, pyridine, water and non-aromatic hydrocarbon material boiling within the range of 90' to 105 C.

4. A process of separating piperidine from pyridine which `comprises fractionally distilling a mixture .containing piperidine, pyridine, fwater C. whereby an azeotropic mixture containing said hydrocarbon, water and aihigherl ratio of pyridine to piperidine than is present in said rst named mixture is distilled 01T, condensing said azeotropic mixture, separating the condensate into a hydrocarbon layer and an aqueous layer and returning a suiiicient amount of at least one of said layers tothe fractionating'. zone to maintain equilibrium therein.

5. A process as speciled in claim 4 in which` the mixture being distilled contains a'lower ratio hydrocarbon vapors of the azeotropic mixture distilled off and in which at leasta portion of the hydrocarbon' layer is returned'to the fractionating zone,

6. A process as speciedin claim 4 in which the mixture being vdistilled contains a lower ratio of water to hydrocarbon than is present in the and hydrocarbon boiling within therange of 80 to water than is present in the f within the range of 80 azeotropic mixture containing water, said hydrovapors of the azeotropic mixture distilled oil' and in which at least a portion of'tgewater layeris returned to the fractionating 'zoilv" 7. A process of cent oi' piperidine and from 20 to 5 per cent of pyridine which comprises fractionally distllling said mixture in the presence of water and nonaromatic hydrocarbon material boiling within the range oi 80 to 110 C. capable of forming an water and a greater ratio of pyridine to piperidine than is present in said iirst named mixture, said azeotropic mixture boiling Abelow the boiling point containing a higher ratio by weight .of piperidine to pyridine than 75 :25 with additional piperidine-pyridine mixture and recovering piperidine and pyridine from the remainder of said distillate.

8. A process of purfying an aqueous distillate containing piperidine and pyridine non-aromatic hydrocarbon, material boiling to 110,C., whereby an carbon and a greater ratio of pyridine to piperidine than is 9. A process as specified .in claim 3 in which the hydrocarbon material contains at least a substantial proportion of parainic material.

10. A process as specified in claim 3 in which the hydrocarbon material contains at least a substantial proportionof cycloparaflinic material,

11. A process as specied in claim 3 in which the hydrocarbon material is a petroleum distillate fraction. I

12. A process of v mixtures containing by weight less than 80 per A range of 30 to 110 c., capable of forming an azeotropic distillate containing the hydrocarbon, water and a greater ratio of pyri- HENRY L. STASSE.

separating piperidine from a Y mixture containing by weight from 80 to 95 perv 

